Art of cracking hydrocarbons



March 12, 1935. w 5 GULLETTE ART oF GRACKING HYDRocARBoNs Filed Dec. 16, 1929 ATTORNEYS Patented Mar. 1.2;, i935 that@ i ortica ART OF CRACKING HYDROCARBONS Willis s. cuneta, Highland, Ina., assignor to Sinclair Refining Company, New York, N. Y., a

corporation of Maine Application December 16,1929, serial No. 414,382

3, Claims.

This invention relates to improvements in the cracking of heavier and higher boiling hydrocarbon oils for the production of lighter and lower boiling hydrocarbon oils'in operations in which 5 the heavier or higher boiling oil is heated to a high Acracking temperature While in the vapor phase. f Y 1 l The invention is of special value and application in conjunction with operations of the type 10 described in an application filed June 13, 1927,

Serial No. 198,621, by Harry L. Pelzer, but the invention is also useful in broader application.

This invention provides particularly improvementsin operationwhich make possible the maintenance of continuously uniform cracking conditions While subjecting raw stock, or diierent raw stocks,'and stocks produced in the operation, heavier or higher boiling than the desired prodf uct but freed from tar produced in the operation, to cracking conditions particularly advantageous with respect to the particular stock.

The complete combined operation of the present invention comprises three general steps; the invention also includes in combinationthe first and second steps, in combination the second and third steps, and in one aspect the thirdstep itself, as Vseparate operations. j Y In carrying out the first two steps oi the improved operation of thisinvention, a stream of 30 raw stock is heated to a high cracking temperature in the vapor phase in a heating conduit, the hot oil products discharged from this heating Yconduit are subjected to a scrubbing operation for the separation of tar and separated tar is discharge from lthis scrubbing operation, the vapors escaping from the scrubbing operation are subjected to a iractionating Y operation in which a condensate formed of constituents higher boiling than suitable as components of the desired product is condensed, none oi this condensate is returned to the rst mentioned heating conduit but'a stream of this condensate is separately heated to a higher cracking temperature in the vapor phase in a separate heating conw duit, the hot oil products discharged from this separate heating conduitare subjected to another scrubbing operation for the separation of tar and separated tar is discharged from this scrubbing operation, the vapors escaping from this scrubbing operation are subjected to another fraction-I ating operation 'in which another condensate formed of constituents higher boiling than suitable as components of the desired product is condensed, none of this condensate is returned to either the rst mentioned or vthe-second mentioned heating conduit, and the desired product is condensed from the vapors escaping from the mentioned fractionating operations. In these two steps of the improved operation ofthe inven- Ation, none of the constituents condensed from the hot oil products discharged from either heating operation is returned, or reluxed, to the heating operation in which such constituents are produced, but the more refractory higher boiling constituents condensed from the hot oil products discharged from the rst heating operation, after separation of tar, Vare urther cracked in the second heating operation in which such constituents Aare subjected to'a higher cracking temperature. Y Y I In carrying out the third step of the-improved operation ofV this invention, a stream of stock, condensate from the fractionating operation in the second step just described for example, is heated to a still higher cracking temperature in the vapor phase in another separate vheating conduitthe hot oil products discharged from this heating conduit are subjected to another scrub- Y bing operation are subjected to another fractionating operation which another condensate formed of constituents higher boiling than suitable as components of the desired produce is condensed, and the desired product is condensed from the vapors escaping from this fractionating operation. In no case is all of the condensate separated in this last mentioned fractionating operation returned, or refluxed, to the last mentioned heating operation, or either'of the previously mentioned heating operations; at least a part of all constituents condensed from the hot oil products discharged from the third heating operation, after separation of tar, is discharged and not returned to any of the heating operations. Advantageously, in accordance with this invention, the condensate separated in the last mentioned fractionating operation is divided into tvvo parts, of lthe same composition or of a common range of constituents, one part is returned to the third heating operation, and none ofthe other part is returned to the third heating operation, or either of the first two heating operations, thereby avoiding accumulation of any high boiling refractory constituent Within the4 operation.

This invention will be further described in connection with the accompanying-drawing which illustrates, diagrammatically and conventionalbingrtower 3a through connection 7a. Oil is suppliedfto the heating conduits 122 and 1c through connections 8 and 9 respectively, by' mea/ns of pumps 10 and 11 respectively,- and the hot oil` products from the heatingv conduits 1b and -lcv are discharged into the scrubbing towers 3b and 3c respectively through vconnections 7br and-y 7c'- respectively. Tar separated in the scrubbing towers 3a, 3b and 3c is discharged therefrom'through connections 12a, 12b and12c respectively. without returning this tar or any part of'this tar, as such, toi any of the heating conduits. Thejvapors escaping from each'of the scrubbingy towers 3a, 3b and 3o pass through connections 13a, 13b and 13o respectively to the iractionating towers 4a; iband 4cxrespectively` in which constituents heavier or higher boiling than suitable as components of. the desired product, freed from tar and suitable for further cracking under appropriate conditions, are condensed. The vapors escaping 'frorneach ofthe ractionating towers 4a,4b and 4c pass through connections 14a, 14h and 14o respectively tosuitable condensingrapparatus for recovery of the desired product,

, either directly or through suitablev treatingor fractionating apparatus. The condensate separated in fractionatingV tower 4a is supplied to pump 10, by which it is forced through heating conduit 1b, through connection i5, and the condensate. separated in fractionatingV tower '4b is supplied'to the` pump' 1'1', by which it is forced through the heatingconduit 1o, through connection 16. The condensate separated inthefractionating tower 4c. is either all' discharged through connectionsA 17, 18V and,19. valve 20.being closed,A or in part, dischargedthrough connection 19` and in part. forced, by meansof pump 21., through the heating conduit lo together with the condensate separated in the fractionating tower lll),` Valves. 20 andv 22 being .appropriately regulated. Rawv oil may also be supplied to the heating conduits 1b` and' 1o through connections 23' and 2 4 respectively. Raw. oil supplied to the heating conduit la may beusedasa cooling me,- dium, and thus. preheated, in the reflux condensers for effecting or controlling condensation in the. several ractionating towers 4a, 4b and 4C, as shown. y

In general,.each of theseveral cracking operations may be carried out as described` in application Serial Number 198,621, mentioned above, except as to the handlingv of high boiling constituents condensed from the hot oil products discharged from the heating operations.

As illustrated, the digesting drums. there describedV may be omitted and the hot oil products tromV the. heating conduitsv may be discharged. directly into-the scrubbing towers. The heatingA furnaces may bey arranged and operated, in, general, as described in this mentioned application. The scrubbing towers may be Varranged.;v and.- operated. for, example, as described an. application filed. March 7th, 1929, Serial Number, 35,199,. by lil.- C. Herthel, Thel vapors escaping from .the fractionating towers may bei.

which raw oil may be circulated as a cooling rne-VA dium, and reflux condensers 26a, 2Gb andV 26o,`

257,958, by E; C.f

through which some extraneous cooling medium such as water may be circulated, o r by means of the'direot introduction of raw oil through connections-27u, 27band-27c, or by means of such introductionofiraw oil supplemented by theoperationof' one or more of the groups of refluxy Scrubbing towers condensers justV mentioned. 3a, 3b and 3c may be controlled by means oi the reflux condensers 28a, 28h and 28o respectively, or by the direct introductionof. raw.` oilgthreugh connections 291:@,29hv andi 29o respectively, or,u by means of such introduction; of raw. oil supplemented by the operation ofthe re'uxf condensers 28a, 28h and 28o.

Inpthe production of. motor fuel, gasolina-fior example, in apparatus' such as that'illustrated,

theheating furnace 2a maybe controlled sothat the hot oil products are dischargedvirom, the f heating conduit,y 1a at atemperature-in theY neighborhood of, ll-lllilo".F.,` theheatingiurnace 2b sol-that the'hot.oil-productsgaredischarged fromA the heatingconduit 112 at a-temperature inthe neighborhood Orino-1130er.,

and the .heating furnace-2cV so that thenotoil products, are discharged from the heating con;- duit 1c at a temperature inthe neighborhooi-l of M50-11.70 F., and the fractionating towers 4b. and 4c may be controlledso--that theternperature of the vapors. escaping, throughoonnections 14a, 14h and 14C respectivelyy approximates 40G-500 F.

In carrying out the yinventioniii-the apparatus illustrated, the condensatesrseparatedjingth successive fractionatingtowers 4cyl!) aifidflo may# be of the same general'boiling range ormay inv clude, successively, increasing proportions ,of v

relatively lower boiling constituents. vThese'con-i densates are, however, heated to successively higher cracking temperatures; ,the condensate fromk the fractionating towers@Y is heated to;v a higher temperature in the heating conduit 1,12( than is theraw oil in the heating cQndu i t;.11a-, and the condensatefrom the fractionating. tower 4b, or the-mixturefof condensates from. the fractionating towersflb and 4c, is heated toa higher temperature in theV heating conduit IothanIisl the condensate-from thefractionatingtower 4a in heating conduit 1b; l

It isv only tothe heating Vconduit 1c that any high boilingl constituents condensed from the hotY oilv products discharged from the heating conduit are returned, but it isv also in the heating conduit 1c that the most severe cracking conditionslare-Y maintained',A It will be appreciated that the ratio between the proportion-of;condensate returned to the heating conduit 1c from ythe fractionatingf tower 4o, andthe-proportion of this condensato discharged' from'the fractionating towerv 4c without return to the heating conduit 1c may varyr Y widely, but in every case at least a part ofa11V Vconstituents condensed from the hot oil products discharged from the heating conduit 1c, following the separation of tar, is discharged without return to the heating conduit la meenerel, .ai greater total production of the desired product is accomlishedby returning twenty per cent., for example, of fthis condensate to the heating conduit than by returning eighty per cent.,`for example, although a higher proportionate yield of the desire'diproduct on the stock treated may be accomplished by 'returningl Vthe higher percentage to the heating conduit. As the ratio is reached at which high boiling reiraotoryconstituents begin-to accumulate within the operation, however, even the proportionate yield of the desired product usually fails to show any material increase. In this aspect, the invention makes it possible to attain the optimum operating balan-ce between stock economy and operating economy.

In the first two steps of the improved operation of this invention, any accumulation of high boiling refractory constituents within the operation is avoided by avoiding any cyclic circulation of such high boiling constituents through the heating operations, high boiling constituents condensed from the hot oil products discharged from the heating operations instead being separately subjected to more severe cracking conditions with respect to which they are relatively less refractory. In the third step ci the improved operation of the invention, any accumulation of high boiling refractory constituents within the operation is avoided by discharging, without return tothe heating operation, at least apart of all high boiling constituents condensed from the hot oil products discharged from the heating operation'.

In one aspect, this last mentioned feature of the operation of the invention is itself an improved cracking operation. By discharging part of all high boiling constituents condensed from the hot oil products discharged from the heating operation, without return to the heating operation, while returning to the heating operation another part of such condensed high boiling constituents, after separation of tar, any continuing accumulation of high boiling refractory constituents within the operation is avoided at the Sametime that a part of the stocks produced in the operation, heavier or higher boiling than the desired product and freed from tar produced in the operation, is resubjected to severe cracking conditions with the recovery of additional quantities of the desired product.

I claim:

1. In cracking operations in which a higher boiling hydrocarbon oil is heated to' a high cracking temperature in the vapor phase, the improvement which comprises heating a stream of raw oil to a high cracking temperature in the vapor phase and subjecting the hot oil products of this heating operation to va scrubbing operation for the separation of tar, separately supplying liquid oil to and withdrawing tar trom the scrubbing operationfsubjecting the vapors escaping fromv the scrubbing operation to a fractionating operation for the condensation of constituents higher boling than suitable as components ofA the desired product and discharging condensate therefrom without returning any of this condensate to said heating operation, separately heating a stream of this condensate to a higher cracking temperature in the vapor phase and subjecting the hot oil products of this separate heating operation to a second scrubbing operation for the separation of tar, separately supplying liquid oil to and withdrawing tar from the second scrubbing operation, subjecting the vapors escaping from the second scrubbing operation to a fractionating operation for the condensation of constituents higher boiling than suitable as cornponente of the desired product and discharging condensateV therefrom without returning any of this condensateto -either of said heating operations, and preventing return to either of said U heating operations of tar withdrawn from either ofsaid -scrubbing operations;

2. In cracking operations in which a higher boiling hydrocarbon oil is heated to a high cracking temperature in the vapor phase, the improvement which comprises heating a stream of raw oil to a high cracking temperature in the vapor .phase and subjecting the hot oil products of this heating operation to a scrubbing operation for the separation of tar, separately supplying liquid oil to and withdrawing tar from the scrubbing operation, subjecting the vapors escaping from the scrubbing operation to a fractionating operation for the condensation of constituents higher` boilingA than suitable as components of the desired product and discharging condensate therefrom without returning any of this condensate to said heating operation, separately heating a stream of this condensate to a higher cracking temperature in the vapor phase and subjecting the hot oil products of this separate heating operation to a second scrubbing operation for the separation of tar, separately supplying liquid oil to and withdrawing tar from said second scrubbing operation, subjecting the vapors escaping from the second scrubbing operation to a fractionating operation for the condensation of constituents higher boiling than suitable as components of the4 desired product and discharging condensate therefrom without-returning any of this condensate to either of said heatingoperations, separately heating a stream of this condensate to a still higher cracking temperature in the vapor phase and subjecting the hot oil products of this further separate heating operation to a third scrubbing operation for the separation of tar, separately supplying liquid oil to and withdrawing tar from said third scrubbing operation, and subjecting the vapors escaping from the third scrubbing operation to a ractionating operation for the condensation of constituents higher boiling than suitable as components of the desired product and discharging condensate therefrom, and preventing return to any of said heating operations of vtar withdrawn from any of said scrubbing operations.

3. In cracking operations in which a higher boiling hydrocarbon oil is heated to a high cracking temperature in the vapor phase, the improvement which comprises heating a stream of oil to a high cracking temperature in the vapor phase and subjecting the hot oil products of this heating operation to' a scrubbing operation for the separation of tar, separately supplying liquid oil to and withdrawing tar from the scrubbing operation, subjecting the vapors escaping from the scrubbing operation to a fractionating operation for the condensation of constituents higher boiling than suitable as components of the desired product and discharging condensate therefrom without returning any of this condensate to said heating operation, separately heating a stream of this condensate to a higher cracking temperature in the vapor phase and subjecting the hot oil products of this separateY heating operation to a second scrubbing operation for the separation of tar, separately supplying liquid oil to and withdrawing tar from said second scrubbing operation, subjecting the vapors escaping from the second scrubbing operation to a fractionating operation for the condensation Vof constituents higher boiling than suitable ascomponents of the desired product, dividing this condensate-into two parts of the same composition and returning one part `of this condensate to the said separate heating operation and discharging the other part of this condensate without returning it to either of said heating operations whereby continuing laccumuu f lation V'ofc high boiling refractory constituents within the operationr is avoided, and preventing return to either of said heating operations offtar withdrawn from operations. Y Y

WILLISYS. GULLE'IFI'E.

either of said scrubbing 5 

